Rear brake imbalance - not balanced

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Stan3
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Re: Rear brake imbalance - not balanced

Post by Stan3 »

so....the saga continues...drums off....check everything...adjust up...drums on...adjust up...back off till free...adjust handbrake up...test drive - this routne I must have repeated twenty plus times now.....

Few miles and NS drum gets very hot....OS slighty warm as it should be

tried without adjusting handbrake back up - same

noticed NS seemed to over-adjusting (back plate slightly convex ie shoes not parallel with drum??)

removed adjuster spring for trip this weekend and adjusted so just to no scuffing.....and marked where adjuster cog was.....50 miles out checked and
same thing had happened - NS very hot....jacked up van and wheel span freely......on way back NS very very hot...NS certainly sizzling spit...jacked up van , wheel span freely....What the blithering heck??

removed drum this evening - adjuster had badjusted itself up half a turn!! shoes show signs of overheating..but wheel still moved freely when jacked up the van...

I could understanding if wheel is binding but it's not.....wheel cylinders release nicely so don't see how it can be the flexible hoses...?

any ideas? whatever I do the NS gets so hot but wheel still turns freely????? really stumping me this one!

thanks for reading!
phil

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937carrera
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Re: Rear brake imbalance - not balanced

Post by 937carrera »

Time for something different then.

The complaint is that the n/s is doing most of the braking.

The rear brakes have a pressure limiting valve. Perhaps that has gone faulty and there is a defect which biases the pressure to the n/s.

I'll confess I don't know the internals, but maybe someone else does and can see a failure mode that would give this effect.

https://www.brickwerks.co.uk/brake-bias-valve-t3.html

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1981 RHD 2.0 Aircooled Leisuredrive project, CU engine
1990 RHD 1.9 Auto Sleeper with DF/DG engine

Stan3
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Re: Rear brake imbalance - not balanced

Post by Stan3 »

thanks, but as I understand the bias valve is located at the front of the vehicle and detrmines the braking pressure delivered to the rear brakes relative to the front dependent on weight being carried in the vehicle......only one pipe comes off the bias valve towards the rear where a union splits to both rear brakes so pressure will/should be equal to each side......

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937carrera
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Re: Rear brake imbalance - not balanced

Post by 937carrera »

In that case forget that idea, I am used to seeing them at the back.

Have you seen this thread ?

Did you have the problem before you started replacing components ?

http://forum.club8090.co.uk/viewtopic.p ... 41e6c0e7d0
1981 RHD 2.0 Aircooled Leisuredrive project, CU engine
1990 RHD 1.9 Auto Sleeper with DF/DG engine

Stan3
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Re: Rear brake imbalance - not balanced

Post by Stan3 »

hi

No sure there wasn't a problem, I'd had the van for 6 years and decided to change shoes, drums and wheel cylinders as the old shoes were worn, not that bad just thought I'd do it as I had gone to the trouble of getting the drums off etc etc.....kibnda wish I hadn't & defintely wish I'd kept the old shoes etc. for comparison!

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937carrera
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Re: Rear brake imbalance - not balanced

Post by 937carrera »

Hmm, a bit more work but good for diagnosis.

Swap everything between n/s and o/s to see if the problem moves or stays on the same corner ?
1981 RHD 2.0 Aircooled Leisuredrive project, CU engine
1990 RHD 1.9 Auto Sleeper with DF/DG engine

Stan3
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Re: Rear brake imbalance - not balanced

Post by Stan3 »

Yeah did that with drums & no difference and also fitted another new pair of shoes, no difference...guess I could change over wheel cylinders but both seem to be working fine....so frustrating!

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937carrera
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Re: Rear brake imbalance - not balanced

Post by 937carrera »

I understand it will be.

you have an unusual problem, you it seems you are going to have to do something different to normal to find out what the problem is. There was no solution in that other thread either.

That'll include swapping over two "good" components.

Do you have a pair of axle stands. Remove all the brake components and run the wheels up for 5 minutes and see what the temps are like. Then repeat with brakes fitted but not adjusted up, then repeat with the brakes correctly adjusted. Don't use the brakes at all while doing these tests.

If there are no temp differences here, then the problem only occurs when the brakes are being used so the finger would then be pointing at the shoes not retracting correctly or different hydraulic pressure being delivered from the wheel cylinders
1981 RHD 2.0 Aircooled Leisuredrive project, CU engine
1990 RHD 1.9 Auto Sleeper with DF/DG engine

Stan3
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Re: Rear brake imbalance - not balanced

Post by Stan3 »

yes, you're right, I've swapped the drums over - just the same. Next thing I'll do is swap the wheel cylinders over....

There must be a logical answer!....however, the one thing that is so weird is the fact that the NS adjuster adusted itself up even without the spring attached (I marked the position of the cog), how does that happen? (the two heavy springs behind the shoes are hooked upwards correctly!) I did a return trip at the weekend of approx 100 miles each way, I stopped a couple of times each way and NS was hotter each time, also jacked up van to check binding - none, a free wheel....when I got home I took off the drum and the shoe had visibly been overheating...

thanks!

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937carrera
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Re: Rear brake imbalance - not balanced

Post by 937carrera »

The automatic adjusters on Clios used to fail regularly, allowing them to unwind. The solution was to put a tiewrap around the bar so that mechanism could not turn. Maybe you could try something like that that or loctite it as a test and then think about why the adjuster is adjusting up ??
1981 RHD 2.0 Aircooled Leisuredrive project, CU engine
1990 RHD 1.9 Auto Sleeper with DF/DG engine

Stan3
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Re: Rear brake imbalance - not balanced

Post by Stan3 »

hi, yes, would like to try that...if i put loctite on the threads will I still have time to get everything back together & adjust up the brakes before it sets?

Highroller
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Re: Rear brake imbalance - not balanced

Post by Highroller »

Have you checked that the near side handbrake cable hasn’t partially seized causing drag on the shoes. From what I’ve read if the hub / drum is getting that hot with no drag then I would suspect the wheel bearings.
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937carrera
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Re: Rear brake imbalance - not balanced

Post by 937carrera »

It depends on the actual product - 10-20 mins is a reasonable cure time. Tie wraps are more temporary and you will still be able to turn the knurled knob to unwind to remove. If you are going down the loctite route, try it first outside of the van - set time and ability to unwind known before everything is assembled.

My earlier suggestion about putting the van on axle stands without brakes was also a test of the wheel bearings
1981 RHD 2.0 Aircooled Leisuredrive project, CU engine
1990 RHD 1.9 Auto Sleeper with DF/DG engine

Stan3
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Joined: 15 Oct 2013, 19:29
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Location: Salisbury, Wiltshire

Re: Rear brake imbalance - not balanced

Post by Stan3 »

thanks both, given that the shoes visibly show signs of onverheating I don't think it could be a bearing problem...it gets so hot so quickly...

Have checked handbrake cables...

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937carrera
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Re: Rear brake imbalance - not balanced

Post by 937carrera »

With where you are I strongly suggest you assume nothing....... you need to be very methodical with the diagnosis
1981 RHD 2.0 Aircooled Leisuredrive project, CU engine
1990 RHD 1.9 Auto Sleeper with DF/DG engine

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